Sultan Ahmed Mosque, known as the Blue Mosque by many tourists because of its bluish interior decoration, is the most important mosque of Istanbul standing next to the Byzantine Hippodrome in the old city center. It was built by the Ottoman sultan Ahmed I between 1609 - 1616 facing Hagia Sophia, in order to compete with it. Its architect was Sedefkar Mehmet Aga, a poet and inlayer as well, and a student of the greatest architect Sinan. When Ahmed I died in 1617, he was buried near the mosque and a mausoleum was built over his tomb.